Back to your original question, Someone at my school did a senior design project on interfacing steering wheel radio controls to IR commands for an aftermarket sony head unit. As I remember, it is a one wire interface with a resistor bank in the steering wheel to select an analog level. Each quantization level corresponded to a command. If you get serious about doing it I'll get more info and even help since it is really easy.

I have a friend that bought an escape and is very happy with it. He takes it off road into the mountains because he is into caving (spelunking?). He mentioned it was a much better value than an explorer because or price/size/features.

Alex Lear